[SCSI] scsi_debug: fix map_region and unmap_region oops

map_region and unmap_region could access to invalid memory area since
they don't check the size boundary.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/scsi_debug.c

@@ -1991,6 +1991,7 @@ static void map_region(sector_t lba, unsigned int len)
 		block = lba + alignment;
 		rem = do_div(block, granularity);
 
+		if (block < map_size)
 			set_bit(block, map_storep);
 
 		lba += granularity - rem;
@@ -2011,7 +2012,8 @@ static void unmap_region(sector_t lba, unsigned int len)
 		block = lba + alignment;
 		rem = do_div(block, granularity);
 
-		if (rem == 0 && lba + granularity <= end)
+		if (rem == 0 && lba + granularity <= end &&
+		    block < map_size)
 			clear_bit(block, map_storep);
 
 		lba += granularity - rem;